Imagine if all the debate over which chemicals were safe and unsafe for humans were suddenly settled. We’d know which products to buy and which to ban. Class action lawsuits filed by communities exposed to pesticides or runoff would be a snap to resolve. A new discovery announced today by researchers at Harvard’s Wyss Institute doesn’t get us all the way there, but it takes us significantly closer. It’s a laboratory-generated, breathing human lung-on-a-chip that mimics the way a real lung allows pathogens to enter the bloodstream.

The device, about the size of a Tostito chip, breathes like a lung and is transparent, allowing researchers to watch for inflammation and make real-time measurements of how much of an aerosolized medication or a toxic substance — or how many nanoparticles, whose health effects are poorly understood — make it into the simulated bloodstream. The lung chip will therefore reduce the need for animal testing. It could also allow environmental health advocates to counter the questionable human-subject research that the pesticide industry fought the EPA to allow. It lost that battle earlier this week.

How it works: The chip, a rubbery polymer, has a network of channels etched into it. The main channel contains one layer of human cells from alveoli — the cavities within the lung where gases move into and out of the bloodstream — and one layer of cells from capillaries that carry oxygen- — and potentially toxin- — rich blood to the rest of the body. As air pressure in the channels flanking the main channel is reduced and increased, the central membrane widens and contracts, simulating breathing.